The present invention relates to a method of cosmetic treatment for combating the effects of skin ageing and to novel cosmetic compositions which are particularly suitable for carrying it out.
The dermo-epidermal junction (DEJ) is known to be a complex structure assuring the cohesion and exchanges between the dermis and epidermis which are essential for the skin to function properly.
It has been discovered that it is possible to slow down or treat skin ageing, and in particular to reduce the depth of wrinkles, and/or slow down their appearance, and/or restore the tonicity and elasticity of the skin, and/or slow down the decrease in tonicity and elasticity of the skin, by means of a method of cosmetic treatment corresponding to a novel concept which consists in using a cosmetically acceptable agent to promote the adhesion of the keratinocytes of the epidermal basal layer to the dermo-epidermal junction, especially to the type IV collagen, also called collagen IV, which is a major constituent of said dermo-epidermal junction. It is this discovery which constitutes the basis of the present invention.
Thus, according to its most general feature, the present patent application aims to cover a method of cosmetic treatment for slowing down or treating skin ageing, and in particular for reducing the depth of wrinkles, and/or slowing down their appearance, and/or restoring the tonicity and elasticity of the skin, and/or slowing down the decrease in tonicity and elasticity of the skin, characterized in that an amount of at least one agent for promoting the adhesion of the keratinocytes of the epidermal basal layer to the dermo-epidermal junction, especially to the collagen IV of said junction, is applied to the skin.
It has furthermore been shown that particularly remarkable results are obtained within the framework of the present invention if the above-mentioned adhesion promoter is applied in association with an effective amount of at least one stimulant of collagen IV synthesis and/or with an effective amount of at least one stimulant of collagen VII synthesis.
The expression xe2x80x9cstimulant of collagen IV or collagen VII synthesisxe2x80x9d is understood within the framework of the present description as meaning any agent which is capable of producing or maintaining a high level of collagen IV in the dermo-epidermal junction, either by increasing the biosynthesis or by inhibiting the enzymes which degrade the constituent proteins of this product.
In one advantageous embodiment of the invention, the above-mentioned adhesion promoter is a divalent metal salt or complex, particularly a magnesium or zinc salt or complex, or a mixture of divalent metal salts or complexes.
The divalent metal salt or complex is preferably a divalent metal chloride or a divalent metal salt or complex with a cosmetically acceptable organic acid such as an amino acid, for example aspartic acid, asparagine, proline, glutamic acid, methionine, leucine, histidine or lysine, or a C2-C12 aliphatic alpha-hydroxy acid, particularly citric acid, glycolic acid, gluconic acid, malic acid, lactic acid or 2-hydroxybutyric acid.
In one currently preferred embodiment of the invention, said divalent metal salt or complex is magnesium aspartate or magnesium chloride.
According to one particular characteristic of the method of the present invention, the above-mentioned adhesion promoter is applied in the form of a composition in which it is present in an amount of between 0.0001 and 5% by weight, preferably of between 0.001 and 1% by weight, based on the total weight of the composition.
Any stimulant of collagen IV synthesis can be used within the framework of the method according to the present invention.
In one currently preferred embodiment, the stimulant of collagen IV synthesis is selected from soya saponins and soya sapogenols, preferably of type A and type B, and plant extracts rich in such compounds, preferably extracts of soya (Glycine max) or alfalfa (Medicago sativa).
In another preferred embodiment, the stimulant of collagen IV synthesis is a whole range of saponins from roots of Medicago sativa. 
Likewise, any stimulant of collagen VII synthesis can be used within the framework of the present invention.
In one currently preferred embodiment, the stimulant of collagen VII synthesis is an extract of Potentilla erecta. 
In another preferred embodiment, the stimulant of collagen VII synthesis is an extract of Bertholletia, particularly Bertholletia excelsa. 
According to a second feature, the present patent application aims to cover novel cosmetic compositions which are particularly suitable for carrying out the method described above.
These compositions are essentially characterized in that they contain an effective amount of at least one agent for promoting the adhesion of the keratinocytes of the epidermal basal layer to the dermo-epidermal junction, especially to the collagen IV of said junction, said agent being selected from magnesium or zinc salts or complexes, in association with an effective amount of at least one stimulant of collagen IV synthesis and/or an effective amount of at least one stimulant of collagen VII synthesis.
In these compositions, the various adhesion promoters and stimulants of collagen IV synthesis or collagen VII synthesis are as described above within the framework of the general description of the method according to the invention.
The compositions of the invention may also advantageously comprise at least one substance for promoting the synthesis of the constituents of the extracellular matrix of the skin.
Furthermore, the compositions according to the invention can also contain at least one substance selected from the group consisting of vitamins, particularly the vitamins of group A (retinol) and group C and derivatives thereof such as the esters, especially the palmitates and propionates, tocopherols, xanthines, particularly caffeine or theophylline, retinoids, particularly vitamin A acid, extracts of Centella asiatica, asiatic and madecassic acids and glycosylated derivatives thereof such as asiaticoside or madecassoside, extracts of Siegesbeckia orientalis, extracts of Commiphora mukul and extracts of Eriobotrya japonica, cosmetically acceptable silicon derivatives such as polysiloxanes, silanols and silicones, C3-C12 aliphatic alpha-keto acids, particularly pyruvic acid, C2-C12 aliphatic alpha-hydroxy acids, particularly citric acid, glycolic acid, malic acid and lactic acid, amino acids, particularly arginine, citrulline and threonine, ceramides, glycoceramides, sphingosine derivatives, particularly type II and III ceramides, phospholipids, forskolin and derivatives thereof, extracts of Coleus, extracts of Tephrosia, elastase inhibitors, particularly ellagic acid and soya peptides, collagenase inhibitors, particularly plant peptides and extracts such as extracts of roots of Coptidis and extracts of roots of Scutellaria baicalensis Georgi, flavonoids such as wogonin, baicalin and baicalein, aqueous-ethanolic extracts of leaves of Ginkgo biloba, Mosla chinensis, Salvia officinalis and Cinnamomum cassia, catechuic extracts of Camellia sinensis and aqueous extracts of bean shells of Theobroma cacao, anti-inflammatories, particularly phospholipase A2 inhibitors, soothing agents, particularly extracts of liquorice, glycyrrhetinic acid and ammonium glycyrrhizinate, hydrating agents, particularly polyols, propylene glycol, butylene glycol, glycerol and hyaluronic acid, agents for combating stretch marks, particularly extracts of horse chestnut and escin, agents for protecting or improving the microcirculation, particularly bioflavonoids from Ginkgo biloba, isodon, extracts of Ami visnaga, visnadine and ruscogenin, free radical inhibitors, particularly polyphenols such as PCO (procyanidolic oligomers) and derivatives thereof and plant extracts, particularly extracts of Curcuma longa, antiseborrhea agents, such as a 5-alpha-reductase inhibitor, particularly an extract of Pygeum africanum, and stimulants of the microcirculation of the blood, such as cepharanthine and methyl nicotinate.
The compositions according to the invention can advantageously contain substances for protecting the skin from the harmful effects of the sun, such as solar filters, individually or in combination, especially UV A filters and UV B filters, particularly titanium oxides and zinc oxides, oxybenzone, Parsol MCX, Parsol 1789 and filters of vegetable origin, substances for limiting the damage caused to the DNA, particularly those for limiting the formation of thymine dimers, such as ascorbic acid and derivatives thereof and/or Photonyl(copyright), and substances for contributing to the elimination of liver spots, such as inhibitors of melanin or tyrosinase synthesis.
Other objects, characteristics and advantages of the invention will become clearly apparent to those skilled in the art from the following explanatory description referring to several Examples relating to tests performed, and Examples of cosmetic formulations, which are given simply by way of illustration and cannot therefore in any way limit the scope of the invention.